1. Field of the Invention
The present invention relates to a power impact tool capable of performing a hammering operation on a workpiece by the striking movement of a tool bit, and more particularly, to a technique of switching between operation modes of the tool bit.
2. Description of the Related Art
Japanese non-examined laid-open Patent Publication No. 2001-62756 discloses a power impact tool capable of performing a hammering operation on a workpiece. The known power impact tool includes a tool bit, a motor for driving the tool bit, an on-off power switch for the motor, a trigger for operating the power switch, and a mode-changing member for switching between respective operation modes of the tool bit. Specifically, the mode-changing member can switch between a hammer mode in which the hammer bit is caused to perform a striking movement and a hammer drill mode in which the hammer bit is caused to perform a combined movement of striking and rotating. The power impact tool further includes an engaging member that can releasably lock the trigger in a depressed position. In order to drive the hammer bit with the mode-changing member in the hammer mode, the trigger is depressed to turn on the power switch and then locked in the depressed position by the engaging member. Thus, in the hammer mode, the tool bit can be caused to perform continuous striking movement without needs of operating the trigger when the trigger is locked in the depressed position by the engaging member. When the lock of the trigger by the engaging member is released, the trigger is allowed to be operated to turn the power switch on and off, so that the tool bit can be caused to perform intermittent striking movement.
However, according to the known power impact tool, in order to effect continuous hammering operation by the tool bit, the user must depress the trigger and then operate the engaging member to lock the trigger in the depressed position every time when trying to drive the hammer bit.